8-Glucosidases localization

Acarbose is an inhibitor of a-glucosidase (localized in the brush border of intestinal epithelium), which liberates glucose from disaccharides. It retards breakdown of carbohydrates, and hence absorption of glucose. Owing to increased fermentation of carbohydrates by gut bacteria, flatulence and diarrhea may develop. Miglitol has a similar effect but is absorbed from the intestine. 

Immunofluorescence techniques have been used to establish the sites of localization of / -glucosidases in spruce hypocotyls (9,61) and chickpea (Cicer arietinum L.) seedlings (46,62,63). In these investigations, the (3-glucosidases were associated with lignified elements (tracheids and endo-dermis tissue), as well as those containing suberin and cutin. 

It is regrettable that Australian chemists failed to discover another local alkaloid, namely castanospermine 3. It was left to an overseas group to collect and extract the seeds from a Queensland legume to yield this valuable alkaloid [6]. Castanospermine seems to display a broad biological activity which surpasses even that of swainsonine, being a particularly powerful competitive inhibitor of both a- and -o-glucosidases [7]. The alkaloid is plentiful enough in the... 

STEVENS, L.H., BLOM, T.J.M., VERPOORTE, R., Subcellular localization of tryptophan decarboxylase, strictosidine synthase and strictosidine glucosidase in suspension cultured cells of Catharanthus roseus and Tabemaemontana divaricata. Plant Cell Rep., 1993,12, 563-576. 

Cyanogenesis is initiated following the hydrolysis of cyanogenic glucosides by 3-glucosidases, which are often referred to as cyanogenic 3-glucosidases. Such enz)mies are localized in the apoplasm, in protein bodies or in... 

Table 3.2 Substrate specificity and localization of cyanogenic j6-glucosidases...

Thayer, S.S. and Gonn, E.E. (1981) Subcellular localization of dhurrin (3-glucosidase and hydroxynitrile lyase in the mesophyll cells of Sorghum leaf blades. Plant Physiol, 67, 617-22. 

Burmeister, G. and Hosel, W. (1981) Immunohistological localization of fj-glucosidases in lignin and isoflavone metabolism in Cicer arietinum (L.) seedlings. Planta, 152, 578-86. 

Marcinowski, S., Falk, H., Hammer, D.K., Hoyer, B. and Grisebach, H. (1979) Appearance and localization of a fi-glucosidase hydrolyzing coniferin in spruce (Picea abies)... 

An interesting thiosugar, salacinol 45, containing sulfur atoms in two different oxidation states was isolated and found to be the active principle of the Indian plant Salacia reticulata which is used in local traditional medicine for treatment of diabetes [96]. The compound was shown to be a potent inhibitor of intestinal a-glucosidases comparable in its activity with the powerful aminosugar derivative acarbose [97]. Kotalanol (46), a chain-extended homolog of salacinol, was discovered around the same time [98]. 

D-Fructose in the human diet derives mainly from sucrose, fruits, and honey. Sucrose is /I-D-fructofuranosyl a-D-glucopyranoside, and, after hydrolysis by invertase (EC 3.2.1.26), to D-glucose and D-fructose, can be absorbed from the small intestine. In the human intestine, invertase, as well as a-D-glucosidases, is developed very early in fetal life, and even appears much earlier than lactase (EC 3.2.1.23). There is no significant, intestinal transport of unhydrolyzed sucrose, and, in animal experiments, sucrose administered by injection is quantitatively excreted in the urine.1 Intestinal invertase is produced by mucosal cells localized in the brush-border membrane of the mucosal epithelia. Invertase is not secreted,1-4 and little or no invertase (sucrase) has been found in the intestinal lumen.1 The specific localization of sucrase at the mucosal, luminal interface is thought to be of functional importance in coupling sucrose digestion to transport.1... 

For the last few years, we have investigated the cellulase components of Pseudomonas fluorescens var. cellulosa in special regard to the physiological relation of their synthesis and localization to the cultural conditions. This pseudomonad is an aerobic mesophilic cellulose-decomposing bacterium isolated earlier by Ueda et al. (39) from field soil. Some of the enzymatic properties of cellulases obtained from it have previously been reported (28). In the present review, the results of our recent studies (42) are described and discussed together with the related works of other authors. [In these studies, activities of cellulase and aryl / -glucosidase were assayed by the same methods as described in a recent paper (31), and that of amylase by the blue value method modified by Fuwa (10)]. 

A 3-D-glucosidase has been isolated from Clostridium thermocellum the enzyme was localized in the periplasmic space. ° It was purified in a five-step procedure including ion-exchange chromatography, gel filtration, and isoelectric... 

Oba, K., E. E. Conn, H. Canut, and A. M. Boudet, Subcellular localization of 2-0-D-glucosyloxy)-cinnamic acids and their related P-glucosidase in the leaves of Melilotus alba Desv., Plant Physiol., 68, 1359-1363 (1981). 

Subcellular localization of 2-(B-Brglucosyloxy)-cinnamic acids and their related 3-glucosidase in leaves of Melilotus alba Desr. Plant Physiol. 

The following step in the biosynthesis of the TIAs consists in the deglycosylation of strictosidine by strictosidine p-glucosidase (SGD) to form the strictosidine aglycone, which is an unstable product rapidly transformed into 4,21-dehydrogeissoschizine (Scheme 4.2). SGD is a glycoprotein localized in the endoplasmic reticulum and is highly specific for strictosidine [21]. This enzyme... 

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